Inter Milan's lead at the top of Serie A has been cut to seven points after a second-half strike by Marcelo Zalayeta saw them go down to a shock defeat at lowly Napoli.
Zalayeta beat Inter goalkeeper Julio Cesar with a first-time shot from the edge of the box after seventy-three minutes to inflict only the third defeat of the season on Jose Mourinho's side.
The defeat coupled with AC Milan's 3-0 victory over Palermo means Inter are seven points ahead of their city rivals with five games to play.
For Napoli, it was their first victory under coach Roberto Donadoni.